1. Field of the Invention
This invention relates to footwear sole construction, and more specifically to sole injection molding for welted construction footwear.
2. Description of the Prior Art
Conventional footwear construction has generally followed two methods, welted construction and molded construction. Welted construction generally stitches an outer sole to an upper to form footwear and thus is labor intensive and therefore expensive. Molded construction generally uses molds and liquid sole material to form the sole onto an upper. This is a less expensive alternative that results in a very durable and flexible outer sole, however the bond between the outer sole and the upper may not be as durable as welted attachment.
Both methods may also attach a midsole to an upper and attach an outer sole thereto using an adhesive. This may be a less expensive alternative, it also produces less satisfactory results.
What is needed is a method that combines the efficiency and durability of molding methods with the quality results of welted construction.
In a first aspect, the present invention provides a perforated midsole for welting to an upper. The midsole may be made of soft woven or other soft to semi-rigid midsole board material. The perforations enable molten outer sole material to flow above the midsole and thus solidly bind a molded outer sole to an upper without the use of conventional adhesives. This technique results in a flexible footwear with a durable outer sole.
In another aspect, the present invention provides a method of mold forming soles onto welted uppers without the use of conventional adhesives.
In a still further aspect, the present invention provides a die-cut midsole having alternative perforation styles and patterns for a midsole according to the present invention. The different patterns are suitable for different outer sole materials and may also result in different wear characteristics.
These and other features and advantages of this invention will become further apparent from the detailed description and accompanying figures that follow. In the figures and description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawings and the description.